The following patents and/or commonly assigned patent applications are hereby incorporated herein by reference:
This invention relates to the field of microelectromechanical systems (MEMS), more particularly to methods of lubricating micromechanical devices.
Micromechanical devices are small structures typically fabricated on a semiconductor wafer using techniques such as optical lithography, doping, metal sputtering, oxide deposition, and plasma etching which have been developed for the fabrication of integrated circuits.
Micromirror devices are a type of micromechanical device. Other types of micromechanical devices include accelerometers, pressure and flow sensors, gears and motors. While some micromechanical devices, such as pressure sensors, flow sensors, and micromirrors have found commercial success, other types have not yet been commercially viable.
Micromechanical devices typically have components that move and contact or rub other parts. Because of the extremely small forces used to move these parts, it is sometimes difficult to overcome the forces resisting the motion of the part. These forces, often called stiction forces, include friction, intermolecular attractive forces such as van der Waals force, and capillary forces created by liquids on the surfaces of the device.
Several techniques help to overcome these stiction forces. Micromechanical device packages typically are hermetically sealed to prevent water vapor and other fluids from entering the package and creating capillary forces. Dissimilar metals and coatings are used to reduce the intermolecular forces. Lubricants, such as perfluorodecanoic acid (PFDA) are also applied to the micromechanical devices to reduce stiction. Lubricants, however, are very difficult to deliver to the surface of a micromechanical device since large quantities of the liquid will dewet the surface of the micromechanical device and may create capillary forces capable of destroying the device. What is needed is a method and apparatus for applying a lubricant to the surface of a micromechanical device that does not destroy the fragile structures of the micromechanical device.
Objects and advantages will be obvious, and will in part appear hereinafter and will be accomplished by the present invention which provides a method and apparatus for applying a lubricant to the surface of a micromechanical device without destroying the fragile structures of the micromechanical device. One embodiment of the invention provides a method of coating the surfaces of a micromechanical device. The method comprising: mixing a coating material with a carrier fluid; nebulizing the mixture to form an aerosol of droplets of the mixture; evaporating a majority of the carrier fluid from the aerosol; exposing the micromechanical device to the evaporated aerosol; and depositing the evaporated droplets of coating material on said micromechanical device.
Another embodiment of the invention provides a method of coating the surfaces of a micromechanical device. The method comprising: mixing a coating material selected from the group consisting of perfluoropolyethers, fluorocarbon oligomers, perfluorinated carboxylic acids, partially fluorinated carboxylic acids, and perfluorodecanoic acid with a carrier fluid selected from the group consisting of perfluorocarbon and hydrofluoroether; nebulizing the mixture to form an aerosol of droplets of the mixture; evaporating a majority of the carrier fluid from the aerosol; exposing the micromechanical device to the evaporated aerosol; and depositing the evaporated droplets of coating material on the micromechanical device.
Another embodiment of the invention provides a method of coating the surfaces of a micromechanical device. The method comprising: mixing a coating material with a carrier fluid selected from the group consisting of perfluorocarbon and hydrofluoroether; nebulizing the mixture to form an aerosol of droplets of the mixture; evaporating a majority of the carrier fluid from the aerosol; exposing the micromechanical device to the evaporated aerosol; and depositing the evaporated droplets of coating material on the micromechanical device.
Another embodiment of the invention provides a method of coating the surfaces of a micromechanical device. The method comprising: mixing a coating material selected from the group consisting of perfluoropolyethers, fluorocarbon oligomers, perfluorinated carboxylic acids, partially fluorinated carboxylic acids, and perfluorodecanoic acid with a carrier fluid; nebulizing the mixture to form an aerosol of droplets of the mixture; evaporating a majority of the carrier fluid from the aerosol; exposing the micromechanical device to the evaporated aerosol; and depositing the evaporated droplets of coating material on the micromechanical device.